Utilizing CO2-activated wollastonite to develop sustainable ternary composite material: CO2 utilization, performance evaluation, and mechanism analysis

초록

To address the escalating global demand for CO₂ reduction and sustainable construction materials, this study investigates a CO₂ conversion and utilization (CCU) strategy to render wollastonite reactive by pre-carbonation and as a CO₂ storage medium. Carbonated wollastonite is used as a limestone substitute to enhance the mechanical and durability performance of a limestone–slag–cement ternary system. Microstructural evolution was examined via isothermal calorimetry, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, mercury intrusion porosimetry, and thermogravimetric analysis. Macroscopic properties were evaluated through compressive and flexural strength, electrical resistivity, and accelerated chloride diffusion tests. Carbonation pretreatment under ambient conditions for 240 h achieved a CO₂ uptake of 0.286 g CO₂/g. Carbonated wollastonite exhibited both carbonate characteristics and pronounced pozzolanic activity due to the formation of amorphous SiO₂, thus providing multifunctional advantages over conventional limestone. The results show that its incorporation refined the microstructure, significantly enhanced early and long-term strength, and improved chloride resistance. Moreover, increased doses enabled partial slag replacement, with 15 % identified as the optimal level. This approach transforms CO₂ from an environmental burden into a performance-enhancing component, thus offering a practical and sustainable upgrade pathway for ternary binder systems. © 2025 Elsevier Ltd

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